Recently, aluminum oxide (Al2O3) has come into the spotlight as a gate insulating film of a transistor or a dielectric of a capacitor. The aluminum oxide has a specific permittivity of about 9 to 11 which exceeds two times a specific permittivity of SiO2, about 3.9. For this reason, as compared with SiO2, the aluminum oxide enables a thin gate insulating film to be formed while suppressing a tunneling current, thereby further contributing to miniaturization of a transistor.
There is a transistor in which aluminum oxide is used for a gate insulating film. In such a transistor, Al2O3 is grown by alternately supplying trimethyl aluminum (TMA: Al(CH3)3) and ozone (O3) within an ALD apparatus, thereby forming the gate insulating film.
In the aforementioned transistor, O3 having high oxidizing power is used as an oxidizing agent for an aluminum film. For this reason, there is an advantage in that although organic aluminum such as TMA is used as a source of the aluminum film, an aluminum oxide film having low carbon concentration can be obtained.
However, since the aluminum film is oxidized using O3 having high oxidizing power, uniformity in film thickness is deteriorated, for example, as compared with a case where the aluminum film is oxidized using O2.